During conventional wellbore drilling sections of the wellbore are drilled and provided with a casing or a liner in subsequent steps. In each step, the drill string is lowered through the casings already installed in the wellbore, and a new section is drilled below the installed casings. By virtue of this procedure, casing which is to be installed in the newly drilled section has to pass through earlier installed casing, therefore the new casing must be of smaller outer diameter than the inner diameter of the earlier installed casing. As a result the available diameter of the wellbore becomes smaller with depth. For deep wells, this consequence can lead to impractically small diameters.
In the description below, references to “casing” and “liner” are made without an implied difference between such types of tubulars. Similarly, references to “lining” can be understood to mean: providing a liner or a casing in the wellbore.
It has been proposed to overcome the problem of stepwise smaller inner diameters of wellbore casing by installing a tubular element in a wellbore and thereafter radially expanding the tubular element to a larger diameter by means of an expander which is pulled, pushed or pumped through the tubular element. However, such method requires that the drill string is to be removed from the wellbore each time a new expandable tubular element is installed in the wellbore.